Conventional throttle bodies and intake manifolds are formed from metals, such as aluminum or steel. They are typically attached to the inlet of an air intake manifold, in a cantilever fashion, by bolts. The bolts, then, support the entire weight of the throttle body. The sealing, of course, is accomplished in a conventional fashion with a flat gasket mounted between the throttle body and intake manifold. These components have been desirable because they are strong and provide accurate flow metering without leaks.
The conventional metal components used within an air intake system, however, are heavier and costlier than desirable. Consequently, with requirements for reduced weight and improved performance of vehicle engines, a desire exists to form more engine components from plastic and/or composite materials. Also, with an emphasis on cost, it is desirable to reduce the number of parts needed to form an assembly and to reduce the service costs by minimizing the time and tools needed for servicing. While plastic and composite intake manifolds are starting to come into use, plastic and composite throttle bodies are not commonly used. The reason is that there are some drawbacks to using these alternative materials over conventional metal components. One drawback is that it is difficult to maintain a long term sealing load on the gasket when using threaded fasteners without the use of metal inserts for receiving the fasteners. While this can be made to work, metal inserts add to the cost and complexity of the molding process. Also, the plastics and composites are generally not as strong as the conventional metals, which must support the assembly adequately. Further, for throttle bodies generally, the dimensional tolerances must be held very tight in order to obtain an accurate amount of desired air flow during engine operation. In order to do this, it is preferable to use a low creep material that is dimensionally stable and will maintain its dimensional tolerances under various humidity and temperature conditions. The conventional metal components have no difficulty achieving the desired results, but plastics and composites do not necessarily perform as well with these desirable characteristics.
Thus, is desirable to provide an intake assembly that improves weight, cost and complexity concerns as compared conventional metal assemblies, but still adequately performs the air flow metering function of the conventional assemblies.